textTools.js

var ADDITIONAL_TEXT_SPACE = 4;

var tools = {};

function measureTextWidth( text, textStyle ){
  // Set a default value
  if ( !textStyle ) {
    textStyle = "text";
  }
  var d = d3.select("body")
      .append("div")
      .attr("class", textStyle)
      .attr("id", "width-test") // tag this element to identify it
      .attr("style", "position:absolute; float:left; white-space:nowrap; visibility:hidden;")
      .text(text),
    w = document.getElementById("width-test").offsetWidth;
  d.remove();
  return w;
}

tools.truncate = function ( text, maxWidth, textStyle, additionalTextSpace ){
  maxWidth -= isNaN(additionalTextSpace) ? ADDITIONAL_TEXT_SPACE : additionalTextSpace;
  if ( isNaN(maxWidth) || maxWidth <= 0 ) {
    return text;
  }
  
  var truncatedText = text,
    newTruncatedTextLength,
    textWidth,
    ratio;
  
  while ( true ) {
    textWidth = measureTextWidth(truncatedText, textStyle);
    if ( textWidth <= maxWidth ) {
      break;
    }
    
    ratio = textWidth / maxWidth;
    newTruncatedTextLength = Math.floor(truncatedText.length / ratio);
    
    // detect if nothing changes
    if ( truncatedText.length === newTruncatedTextLength ) {
      break;
    }
    
    truncatedText = truncatedText.substring(0, newTruncatedTextLength);
  }
  
  if ( text.length > truncatedText.length ) {
    return text.substring(0, truncatedText.length - 3) + "...";
  }
  return text;
};


module.exports = function (){
  return tools;
};